Throughout the life of a spacecraft, attitude modifications are made to carry out mission objectives, to determine orientation, and to correct for undesired torques. In order to minimize expendable fuel in slewing maneuvers, reaction wheel systems are used to transfer rotational momentum to and from the satellite body.
In performing attitude modification slews, conditions may arise that prevent the maneuver from being successful. One such condition is when the total system momentum exceeds the storage capability of the reaction wheel assembly. What is needed is a method and system of controlling the spacecraft in the presence of momentum saturation. Spacecraft health must be ensured by providing a safe power situation and to allow periodic telemetry and command (T&C) visibility to the ground. The spacecraft should be controllable even if the reaction wheel assembly is partially inoperative.